NGINX is a webserver (not DNS).
I recommend you avoid setting up your own DNS Servers and instead use a Service like Amazon's Route 53 or Zerigo. This will save you time so you can focus on problems that are not easily solved with a few dollars a month.
If you want to run your own DNS Server have a look at this thread
In re-reading your question. I think you may be asking how to host multiple websites in NGiNX from the same server, if that is your question, use VirtualHosts. Heres a good tutorial for ubuntu. After setting up the virtual hosts, you will need to add the domain and records to the DNS Service provider of your choice, and point your domain to those nameservers from your domain registrar (Godaddy, eNom, etc.)
Also please avoid cross posting to multiple StackExchange sites: